Self-supporting electrocatalytic material and preparation method thereof

ABSTRACT

The present disclosure relates to a self-supporting electrocatalytic material and a preparation method thereof, the self-supporting electrocatalytic material is a Cu 2 O/WO 3 /CF self-supporting electrocatalytic material. The Cu 2 O/WO 3 /CF self-supporting electrocatalytic material comprises: a foamed copper substrate, and Cu 2 O and WO 3  grown in situ on the foamed copper substrate.

TECHNICAL FIELD

The present disclosure relates to a self-supporting electrocatalyticmaterial, in particular to a Cu₂O/WO₃/CF self-supportingelectrocatalytic material and a NiOOH/Cu₂O/WO₃/CF self-supportingelectrocatalytic material and a preparation method thereof, whichbelongs to the technical field of composite materials.

BACKGROUND

The electrochemical decomposition of water into hydrogen and oxygen isan effective method for fundamentally realizing the strategy of theconversion and storage of renewable energy, and solving the globalenergy and environmental problems. In this process, the conversionefficiency is limited by the high overpotential. At present, the noblemetal Pt-based materials are considered to be the most effectivehydrogen evolution reaction (HER) electrocatalysts, and Ir/Ru and itsoxides are considered to show excellent oxygen evolution reaction (OER)electrocatalytic properties in both acidic and alkaline electrolytes.However, due to the low content of these precious metal materials in theearth crust and the high cost, their commercial large-scale applicationhas been limited. The development of new sustainable non-noble metalelectrocatalytic materials with low cost and high efficiency is the key.

WO₃ belongs to n-type semiconductors, which are composed of regularoctahedral perovskite units, have unique optical, electronic, andchemical properties, and have been widely used in sensors, catalysis,electrochromic, and other fields in recent years. WO₃ material has afast electron transfer speed (12 cm² V⁻¹s⁻¹), a suitable hole diffusionlength (150 nm), and a wide light absorption range (12%). Therefore, WO₃is a promising photoelectric catalytic material. However, the WO₃nanomaterial obtained by current research has some shortcomings such asa small specific surface area, few catalytic active sites, high andunstable hydrogen and oxygen production over-potential, which limitstheir catalytic activity. Oxygen defects in metal oxides act as activesites to improve conductivity and facilitate the adsorption anddesorption of water molecules or intermediate reaction substances (forexample, .H in HER; .OH and .OOH in OER), thereby further illustratingthat the introduction of oxygen defects into WO₃ materials is expectedto improve the electrocatalytic performance of WO₃ materials. At thesame time, through processes such as compounding, the electronicstructure of WO₃ is adjusted, the oxygen defect content can beeffectively increased, so that the electrocatalytic active sites areincreased and the electrocatalytic performance is optimized.

At present, the use of copper-based materials for oxygen evolutioncatalysts has attracted wide attention. Copper-based materials have theadvantages of abundant reserves, low cost, and simple synthesis of theircompounds. Cu-based metal oxides are good electrode materials. However,although Cu₂O materials are used as photocatalytic materials, there arerelatively few studies on their use in electrocatalysis. Therefore, itis necessary to further research and explore Cu₂O electrocatalyticmaterials. In addition, in order to avoid the influence of the binder onthe conductivity and active area of the catalyst during the preparationof the working electrode, the direct synthesis of WO₃ nanostructuredcatalyst on the conductive substrate can effectively improve theelectrocatalytic performance. Foamed copper with high abundance and lowprice has attracted widespread attention, because of its large specificsurface area, high electronic conductivity, and ideal 3D open cellstructure, it is widely used as a support system for electrodematerials.

Foamed copper is a new multifunctional material with a large number ofconnected or unconnected pores uniformly distributed in the coppermatrix. Foamed copper has good conductivity and ductility, and itspreparation cost is lower than that of foamed nickel, and itsconductivity is better than that of foamed nickel. It is a potentialmulti-dimensional carrier for the preparation of battery anodematerials, catalysts, and electromagnetic shielding materials. Comparedwith metal materials, there are many advantages to using highlyconductive carbon materials (such as carbon fiber, carbon cloth, carbonpaper, etc.) as a carrier, such as their light weight, stable chemicalproperties, and environmental friendliness, etc. However, due to theirgood chemical inertness, the compatibility between carbon materials andvarious inorganic materials is poor, so it is difficult to directly andeffectively grow active substances on their surfaces. Therefore, it isof great significance to develop an effective method to directly grow ahighly active composite material on the foamed copper conductivesubstrate and directly use it for electrocatalytic hydrogen production.

SUMMARY

In view of the above problems, the present disclosure provides a newself-supporting electrocatalytic material and a preparation methodthereof. The purpose of the present disclosure is to synthesize ahigh-efficiency hydrogen evolution reaction (HER) electrocatalyticmaterial by adopting a multi-step method, and the structure of theprepared self-supporting electrocatalytic material is controllable, andthe product has the structure of a nanowire (WO₃) regular tetrahedron(Cu₂O) and ultra-small nanoparticles (NiOOH) at the same time, and thestructures of nanowire, regular tetrahedron and ultra-small nanoparticleare uniformly distributed. The prepared material shows betterelectrocatalytic performance in neutral solution.

In a first aspect, the present disclosure provides a Cu₂O/WO₃/CFself-supporting electrocatalytic material, comprising: a foamed coppersubstrate, and Cu₂O and WO₃ grown in situ on the foamed coppersubstrate.

According to the present disclosure, the foamed copper is used as acopper source for the first time, and a Cu₂O tetrahedral structure and aWO₃ nanowire structure are grown in situ on the surface of the foamedcopper substrate by a one-step method, so that the influence of anadhesive on the conductivity and activity of the catalyst during thepreparation of a working electrode is avoided, and the electrocatalyticperformance can be effectively improved.

Preferably, the total loading capacity of Cu₂O and WO₃ is 0.5 to 4mg/cm².

Preferably, the molar ratio of WO₃ and Cu₂O is 1:(0.5 to 1).

In a second aspect, the present disclosure provides a Cu₂O/WO₃/CFself-supporting electrocatalytic material. The Cu₂O/WO₃/CFself-supporting electrocatalytic material also includes NiOOH grown insitu on the foamed copper substrate, which is designed as aNiOOH/Cu₂O/WO₃/CF self-supporting electrocatalytic material. In otherwords, the NiOOH/Cu₂O/WO₃/CF self-supporting electrocatalytic materialcomprises: a foamed copper substrate, and NiOOH, Cu₂O, and WO₃ grown onthe foamed copper substrate. Among them, NiOOH nanoparticles aredistributed in both Cu₂O and WO₃.

In the present disclosure, the foamed copper substrate (CF) can improvethe exposure of active sites of products due to its high specificsurface, high electronic conductivity and 3D open-cell structure, whichis beneficial to the improvement of electrocatalytic performance.Therefore, the Cu₂O tetrahedron structure is grown in situ by taking thefoamed copper as the copper source for the first time, and the NiOOH andWO₃ are directly grown on the foamed copper substrate (CF) at the sametime, so that the influence of the adhesive on the conductivity andactivity of the catalyst during the preparation of the working electrodeis avoided and the electrocatalytic performance can be effectivelyimproved by utilizing the synergistic effect.

Preferably, the total loading capacity of NiOOH, Cu₂O, and WO₃ in theCu₂O/WO₃/CF self-supporting electrocatalytic material is 0.5 to 4mg/cm².

Preferably, the molar ratio of WO₃, Cu₂O, and NiOOH is 1:(0.5 to1):(0.01 to 0.05).

In a third aspect, the present disclosure also provides a preparationmethod of the above mentioned Cu₂O/WO₃/CF self-supportingelectrocatalytic material, comprising:

(1) dissolving a tungsten source in absolute ethanol to obtain a firstsolution;

(2) immersing the foamed copper in a high-pressure reaction kettlecontaining the first solution, reacting at 100 to 200° C. for 1 to 36hours, and then centrifuging, washing, and drying to obtain theCu₂O/WO₃/CF self-supporting electrocatalyst material.

Preferably, the tungsten source is selected from at least one of theammonium tungstate (NH₄)₆W₇O₂₄.6H₂O, ammonium paratungstate(NH₄)₁₀[H₂W₁₂O₄₂], ammonium metatungstate (NH₄)₆H₂W₁₂O₄₀, tungstenisopropoxide W(OCH(CH₃)₂)₆, and tungsten hexachloride WCl₆; theconcentration of the tungsten source in the first solution is 0.01 to 5mol/L.

Preferably, the volume filling ratio of the high-pressure reactionkettle containing the first solution is 20 to 60%.

In a fourth aspect, the present disclosure also provides a preparationmethod of the above mentioned Cu₂O/WO₃/CF self-supportingelectrocatalytic material, comprising:

(1) dissolving a tungsten source in absolute ethanol to obtain the firstsolution;

(2) immersing the foamed copper grown with NiOOH and Cu₂O in ahigh-pressure reaction kettle containing the first solution, reacting at100 to 200° C. for 1 to 36 h, and then centrifuging, washing, and dryingto obtain a NiOOH/Cu₂O/WO₃/CF self-supporting electrocatalytic material.

Preferably, the concentration of the tungsten source in the firstsolution is 0.01 to 5 mol/L.

Preferably, the tungsten source is selected from at least one ofammonium tungstate (NH₄)₆W₇O₂₄.6H₂O, ammonium paratungstate(NH₄)₁₀[H₂W₁₂O₄₂], ammonium metatungstate (NH₄)₆H₂W₁₂O₄₀, tungstenisopropoxide W(OCH(CH₃)₂)₆, and tungsten hexachloride WCl₆.

Preferably, the volume filling ratio of the high-pressure reactionkettle containing the first solution is 20 to 60%.

Preferably, the foamed copper grown with NiOOH and Cu₂O is prepared by:

(1) dissolving a nickel source in water to obtain a second solution;

(2) immersing the foamed copper in a high-pressure reaction kettlecontaining the second solution, reacting at 160 to 200° C. for 6 to 12hours, and then washing and drying to obtain the foamed copper withNiOOH and Cu₂O.

Also, preferably, the nickel source is selected from at least one ofnickel acetate Ni(CH₃COO)₂, nickel oxalate dihydrate NiC₂O₄.2H₂O, nickelchloride hexahydrate NiCl₂.6H₂O, and nickel nitrate hexahydrateNiN₂O₆.6H₂O; the concentration of the nickel source is 0.01 to 5 mol/L;

Preferably, the volume filling ratio of the high-pressure reactionkettle containing the second solution is 20 to 80%.

Beneficial Effects

(1) The NiOOH/Cu₂O/WO₃ composite material is synthesized by a two-stepmethod in the present disclosure. The Cu₂O is in situ synthesized withfoamed copper as a raw material, and the composite material is directlygrown on the foamed copper substrate; at the same time, the Cu₂O and WO₃are directly grown on the foamed copper by a one-step method in thepresent disclosure;

(2) the present disclosure has mild reaction condition, easyrealization, and easy control of the process;

(3) the composite material prepared by the present disclosure has alarge number of oxygen defects;

(4) the NiOOH/Cu₂O/WO₃ self-supporting electrocatalytic materialprepared by the present disclosure exhibits better electrocatalyticperformance in a neutral electrolyte.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows X-ray diffraction (XRD) spectra of NiOOH/Cu₂O/WO₃/CF,Cu₂O/WO₃/CF and NiOOH/Cu₂O/CF prepared under the conditions of Example1, Comparative Example 1, and Example 5;

FIG. 2 shows scanning electron microscope (SEM) photographs of (a-b)NiOOH/Cu₂O/CF and (c-d) Cu₂O/WO₃/CF prepared under the conditions ofComparative Example 1 and Example 5;

FIG. 3 shows a SEM photograph of NiOOH/Cu₂O/WO₃/CF prepared under theconditions of Example 1;

FIG. 4 shows a transmission electron microscopy (TEM) andhigh-resolution transmission electron microscopy (HRTEM) image ofNiOOH/Cu₂O/WO₃/CF prepared under the conditions of Example 1;

FIG. 5 shows a distribution diagram of corresponding elements ofNiOOH/Cu₂O/WO₃/CF prepared under the conditions of Example 1;

FIG. 6 shows the O1s spectra of NiOOH/Cu₂O/WO₃/CF, Cu₂O/WO₃/CF, andNiOOH/Cu₂O/CF prepared under the conditions of Example 1, ComparativeExample 1, and Example 5;

FIG. 7 shows a comparative graph of the electrocatalytic hydrogenproduction overpotentials at different current densities forNiOOH/Cu₂O/WO₃/CF, Cu₂O/WO₃/CF, NiOOH/Cu₂O/CF, and CF prepared under theconditions of Example 1, Comparative Example 1, and Example 5.

FIG. 8 shows a Raman spectrum of NiOOH/Cu₂O/WO₃/CF prepared under theconditions of Example 1.

DETAILED DESCRIPTION

The present disclosure will be further described below through thefollowing embodiments. It should be understood that the followingembodiments are only used to illustrate the present disclosure, not tolimit the present disclosure.

In this disclosure, for the first time, NiOOH, Cu₂O and WO₃ arecompounded and directly grown on foamed copper by a two-step method toprepare a NiOOH/Cu₂O/WO₃/CF self-supporting electrocatalytic materialrich in oxygen defects. Among them, the optimal total loading capacityof NiOOH/Cu₂O/WO₃ is 0.5 to 4 mg/cm². The molar ratio of WO₃, Cu₂O, andNiOOH is 1:(0.5 to 1):(0.01 to 0.05).

The following exemplarily illustrates the preparation method of theNiOOH/Cu₂O/WO₃/CF self-supporting electrocatalytic material.

Cleaning of the foamed copper substrate. Take a 50 mL beaker, andcompletely immerse the foamed copper with a length of 3 to 7 cm and awidth of 1 to 2 cm into acetone, HCl solution of 2 to 6 mol/L, deionizedwater, and absolute ethanol in sequence, and carry out ultrasonictreatment for 15 to 30 minutes respectively.

Preparation of foamed copper grown with NiOOH/Cu₂O. The type,concentration, and reaction temperature of the selected nickel source inthe present disclosure are very important. The target product phase thatis not suitable for the preparation cannot be synthesized, and theproduct loading is too large or too small, so that the product isdifficult to directly grow on the foamed copper or cause the compositeproduct to fall off from the foamed copper in the subsequent compositesynthesis stage.

The analytically reagent nickel acetate Ni(CH₃COO)₂ is added as a nickelsource to 20 to 80 mL of deionized water, and stirred for 20 to 60minutes to form a uniformly mixed solution A. Among them, the nickelsource can also be selected from nickel acetate Ni(CH₃COO)₂, nickeloxalate dihydrate NiC₂O₄.2H₂O, nickel chloride hexahydrate NiCl₂.6H₂O,and nickel nitrate hexahydrate NiN₂O₆.6H₂O, etc. The concentration of Nisource in the solution A can be 0.01 to 5 mol/L.

The foamed copper is immersed in a polytetrafluoroethylene-linedautoclave containing the solution A and sealed, and the volume fillingratio keeps between 20% and 80%. Putting the sealed high-pressurereactor into a homogeneous hydrothermal reactor, the temperatureparameter can be set to 160 to 200° C., and the reaction time can be 6to 12 hours.

After the reaction is completed, cooling to room temperature, and thencentrifuging, washing, and drying to obtain foamed copper withNiOOH/Cu₂O grown on the surface. Among them, washing includes washingwith deionized water 3 to 5 times. Among them, drying includes puttingthe washed foamed copper into a 50 to 70° C. vacuum oven and drying for5 to 8 hours, or putting in a freeze drying oven at −40 to −60° C. for 5to 8 hours.

As a tungsten source, analytical reagent ammonium tungstate(NH₄)₆W₇O₂₄.6H₂O is dissolved and added to 20 to 80 mL of absoluteethanol, and stir for 20 to 60 minutes to form a uniformly mixedsolution B. Among them, the tungsten source can also be selected fromone of ammonium tungstate (NH₄)₆W₇O₂₄.6H₂O, ammonium paratungstate(NH₄)₁₀[H₂W₁₂O₄₂]xH₂O, ammonium metatungstate (NH₄)₆H₂W₁₂O₄₀.XH₂O, andtungsten isopropoxide W(OCH(CH₃)₂)₆ and tungsten hexachloride WCl₆, etc.The concentration of the tungsten source in the solution B can be 0.01to 5 mol/L.

The NiOOH/Cu₂O-grown foamed copper or pure foamed copper is immersed ina polytetrafluoroethylene lined autoclave containing the solution B andsealed, and the volume filling ratio is maintained between 20% and 60%.Putting the sealed high-pressure reactor into a homogeneous hydrothermalreactor, the temperature parameter can be set to 100 to 200° C., and thereaction time can be 1 to 36 hours.

After the reaction is completed, cooling to room temperature, and thencentrifuging, washing, and drying to obtain foamed copper grown withNiOOH/Cu₂O/WO₃ or foamed copper grown with Cu₂O/WO₃. Among them, washingincludes washing with deionized water 3 to 5 times. Among them, dryingincludes putting the washed foamed copper into a vacuum oven at 50 to70° C. and drying for 5 to 8 hours, or putting in a freeze drying ovenat −40 to −60° C. for 5 to 8 hours.

Hereinafter, the present disclosure will be further described with thefollowing examples. It should be understood that the following examplesare used to explain this invention and do not mean to limit the scope ofthis invention. Any non-essential improvements and modifications made bya person skilled in the art based on this invention all fall into theprotection scope of this invention. The specific process parametersbelow are only exemplary, and a person skilled in the art can chooseproper values within an appropriate range according to the description,and are not restricted to the specific values shown below.

Example 1

(1) Prepared a nickel acetate Ni(CH₃COO)₂.4H₂O solution A with aconcentration of 0.05 mol/L. Specifically, Ni(CH₃COO)₂.4H₂O was added to40 mL of deionized water and stirred for 30 minutes to form a uniformlymixed solution A;

(2) Put the solution A into a polytetrafluoroethylene lined autoclave,the volume filling ratio was maintained at 40%;

(3) Took a 50 mL beaker, and completely immerse the foamed copper with alength of 6 cm and a width of 1 cm into acetone, 3 mol/L HCl solution,deionized water, and absolute ethanol in sequence, and carried outultrasonic treatment separately for 30 minutes. Put the processed foamedcopper into a polytetrafluoroethylene reactor containing the solution A;put the sealed reactor into a homogeneous hydrothermal reactor, thetemperature parameter was set to 160° C., and the reaction time was 12hours;

(4) After the reaction was completed and cooled to room temperature, thefoamed copper after the reaction was taken out and washed with absoluteethanol and deionized water 3 times;

(5) Prepared a solution B of tungsten hexachloride WCl₆ with aconcentration of 0.05 mol/L. Specifically, added WCl₆ to 40 mL ofdeionized water and stirred it for 30 minutes to form a uniformly mixedsolution B;

(6) Immersed the NiOOH/Cu₂O-grown foamed copper in apolytetrafluoroethylene lined autoclave containing the solution B andsealed it, and the volume filling ratio was maintained at 40%. Put thesealed autoclave into a homogeneous hydrothermal reactor, thetemperature parameter was set to 160° C., and the reaction time was 12hours;

(7) After the reaction was completed, cooled to room temperature, tookout the foamed copper after the reaction, and washed with absoluteethanol and deionized water 3 times. Put it into a 60° C. vacuum oven ora freeze-drying oven to dry for 6 hours to obtain a NiOOH/Cu₂O/WO₃/CFself-supporting electrocatalytic material. The total loading ofNiOOH/Cu₂O/WO₃ was 0.86 mg/cm². The molar ratio of WO₃ and Cu₂O was1:0.5. The molar ratio of WO₃, Cu₂O, and NiOOH was 1:0.5:0.01.

Example 2

(1) Prepared a nickel acetate Ni(CH₃COO)₂.4H₂O solution A with aconcentration of 1 mol/L. Specifically, Ni(CH₃COO)₂.4H₂O was added to 60mL of deionized water and stirred for 30 minutes to form a uniformlymixed solution A;

(2) Put the solution A into a polytetrafluoroethylene lined autoclave,the volume filling ratio was maintained at 60%;

(3) Took a 50 mL beaker, and completely immersed the foamed copper witha length of 6 cm and a width of 2 cm in acetone, 4 mol/L HCl solution,deionized water, and absolute ethanol in sequence, and carried outultrasonic treatment separately for 30 minutes. Put the processed foamedcopper into a polytetrafluoroethylene reactor containing the solution A;put the sealed reactor into a homogeneous hydrothermal reactor, thetemperature parameter was set to 200° C., and the reaction time was 12hours;

(4) After the reaction was completed and cooled to room temperature, thefoamed copper after the reaction was taken out and washed with absoluteethanol and deionized water 3 times.

(5) Prepared a solution B of ammonium tungstate (NH₄)₆W₇O₂₄.6H₂O with aconcentration of 1 mol/L. Specifically, added (NH₄)₆W₇O₂₄.6H₂O to 40 mLof deionized water and stirred it for 30 minutes to form a uniformlymixed solution B;

(6) Immersed the NiOOH/Cu₂O-grown foamed copper in apolytetrafluoroethylene lined autoclave containing the solution B andsealed it, and the volume filling ratio was maintained at 40%. Put thesealed autoclave into a homogeneous hydrothermal reactor, thetemperature parameter was set to 140° C., and the reaction time was 24hours;

(7) After the reaction was completed and cooled to room temperature, thefoamed copper after the reaction was taken out and washed with absoluteethanol and deionized water 3 times. Put it into a 60° C. vacuum oven ora freeze-drying oven to dry for 6 hours to obtain a NiOOH/Cu₂O/WO₃/CFself-supporting electrocatalytic material. The total loading ofNiOOH/Cu₂O/WO₃ in the obtained NiOOH/Cu₂O/WO₃/CF self-supportingelectrocatalytic material was 1.5 mg/cm². The molar ratio of WO₃, Cu₂O,and NiOOH was 1:0.3:0.03.

Example 3

(1) Prepared a nickel oxalate dihydrate NiC₂O₄.2H₂O solution A with aconcentration of 3 mol/L. Specifically, NiC₂O₄.2H₂O was added to 50 mLof deionized water and stirred for 30 minutes to form a uniformly mixedsolution A;

(2) Put the solution A into a polytetrafluoroethylene lined autoclave,the volume filling ratio was maintained at 50%;

(3) Took a 50 mL beaker, and completely immersed the foamed copper witha length of 7 cm and a width of 1 cm into acetone, 3 mol/L HCl solution,deionized water, and absolute ethanol in sequence, and carried outultrasonic treatment separately for 30 minutes. Put the processed foamedcopper into a polytetrafluoroethylene reactor containing the solution A;put the sealed reactor into a homogeneous hydrothermal reactor, thetemperature parameter was set to 180° C., and the reaction time was 18hours;

(4) After the reaction was completed and cooled to room temperature, thefoamed copper after the reaction was taken out and washed with absoluteethanol and deionized water for 3 times;

(5) Prepared a solution B of tungsten hexachloride WCl₆ with aconcentration of 4 mol/L. Specifically, added WCl₆ to 60 mL of deionizedwater and stirred it for 30 minutes to form a uniformly mixed solutionB;

(6) Immersed the NiOOH/Cu₂O-grown foamed copper in apolytetrafluoroethylene lined autoclave containing the solution B andsealed it, and the volume filling ratio was maintained at 60%. Put thesealed autoclave into a homogeneous hydrothermal reactor, thetemperature parameter was set to 140° C., and the reaction time was 30hours;

(7) After the reaction was completed, cooled to room temperature, tookout the foamed copper after the reaction, and washed with absoluteethanol and deionized water 3 times. Put it into a 60° C. vacuum oven ora freeze-drying oven to dry for 6 hours to obtain a NiOOH/Cu₂O/WO₃/CFself-supporting electrocatalytic material. The total loading ofNiOOH/Cu₂O/WO₃ was 3 mg/cm². The molar ratio of WO₃, Cu₂O, and NiOOH was1:0.6:0.05.

Example 4

(1) Prepared a nickel nitrate hexahydrate NiN₂O₆.6H₂O solution A with aconcentration of 4 mol/L. Specifically, NiN₂O₆.6H₂O was added to 80 mLof deionized water and stirred for 30 minutes to form a uniformly mixedsolution A;

(2) Put the solution A into a polytetrafluoroethylene lined autoclave,the volume filling ratio was maintained at 80%;

(3) Took a 50 mL beaker, and completely immersed the foamed copper witha length of 5 cm and a width of 2 cm into acetone, 6 mol/L HCl solution,deionized water, and absolute ethanol in sequence, and carried outultrasonic treatment separately for 30 minutes. Put the processed foamedcopper into a polytetrafluoroethylene reactor containing the solution A;put the sealed reactor into a homogeneous hydrothermal reactor, thetemperature parameter was set to 160° C., and the reaction time was 6hours;

(4) After the reaction was completed and cooled to room temperature, thefoamed copper after the reaction was taken out and washed with absoluteethanol and deionized water 3 times;

(5) Prepared a solution B of tungsten isopropoxide W(OCH(CH₃)₂)₆ with aconcentration of 2 mol/L. Specifically, added W(OCH(CH₃)₂)₆ to 40 mL ofdeionized water and stirred it for 30 minutes to form a uniformly mixedsolution B;

(6) Immersed the NiOOH/Cu₂O-grown foamed copper in apolytetrafluoroethylene lined autoclave containing the solution B andsealed it, and the volume filling ratio was maintained at 40%. Put thesealed autoclave into a homogeneous hydrothermal reactor, thetemperature parameter was set to 160° C., and the reaction time was 24hours;

(7) After the reaction was completed and cooled to room temperature, thefoamed copper after the reaction was taken out and washed with absoluteethanol and deionized water 3 times. Put it into a 60° C. vacuum oven ora freeze-drying oven to dry for 6 hours to obtain a NiOOH/Cu₂O/WO₃/CFself-supporting electrocatalytic material. The total loading ofNiOOH/Cu₂O/WO₃ was 2.8 mg/cm². The molar ratio of WO₃ and Cu₂O was1:0.5. The molar ratio of WO₃, Cu₂O, and NiOOH was 1:0.55:0.03.

Example 5

The preparation process of the Cu₂O/WO₃/CF electrocatalytic material inExample 5 referring to Example 1, the difference was that the Cu₂O/WO₃foamed copper was obtained only by a one-step solvothermal method, thatis, only the steps of step 5 to step 7 in Example 1 were performed, andwhat was added in step 6 was the foamed copper that had not grownanything. In the obtained Cu₂O/WO₃/CF self-supporting electrocatalyticmaterial, the loading capacity of Cu₂O/WO₃ was 0.7 mg/cm², and the molarratio of WO₃ and Cu₂O was 1:0.5.

Comparative Example 1

The preparation process of the NiOOH/Cu₂O/CF self-supportingelectrocatalytic material in this comparative example 1 referred toExample 1, the difference was that the foamed copper grown withNiOOH/Cu₂O was obtained only by one-step hydrothermal method, that is,only the steps of 1 to 4 of the Example 1 was performed, thesolvothermal reaction process of the steps 5 to 7 was not performed. Inthe obtained NiOOH/Cu₂O/CF self-supporting electrocatalytic material,the loading capacity of NiOOH/Cu₂O was 0.28 mg/cm². The molar ratio ofNiOOH and Cu₂O was 0.02:1.

FIG. 1 shows the X-ray diffraction (XRD) spectra of NiOOH/Cu₂O/WO₃/CF,Cu2O/WO3/CF, and NiOOH/Cu2O/CF prepared under the conditions of Example1, Comparative Example 1, and Example 5, It can be seen from the figurethat no other miscellaneous phases exist in the phase synthesized by theinvention.

FIG. 2 shows the scanning electron microscope (SEM) photographs ofNiOOH/Cu₂O/CF and Cu₂O/WO₃/CF prepared under the conditions ofComparative Example 1 and Example 5. It can be seen that the NiOOH/Cu₂Oin Comparative Example 1 are large particles formed by agglomeration ofmany small nanoparticles dispersing in the rough surface structure. TheCu₂O/WO₃ in Example 5 was a composite structure uniformly dispersed byWO₃ nanowires and Cu₂O tetrahedra. These tetrahedrons were of the samesize and were entangled by the interwoven nanowire structure at the sametime.

FIG. 3 to FIG. 5 respectively show the SEM photos of NiOOH/Cu₂O/WO₃/CFprepared under the conditions of Example 1, and the element distributionof the tetrahedron and nanowire structure in the NiOOH/Cu₂O/WO₃/CFstructure. It can be seen that the microstructure of NiOOH/Cu₂O/WO₃grown in foamed copper was similar to Cu₂O/WO₃ (FIG. 3). The mainelements of the tetrahedron were Cu and O, which further proved that thetetrahedral structure was Cu₂O, the nanowire structure was WO₃ (FIG. 5),combined with XRD; in addition, it can be seen from FIG. 4 that NiOOHand Cu₂O nanoparticles were uniformly dispersed in the material. Theheterojunction surface formed by this WO₃/Cu₂O/NiOOH hierarchicalstructure was very important for the improvement in electrocatalyticperformance.

FIG. 6 shows the O1s spectra of NiOOH/Cu₂O/WO₃/CF, Cu₂O/WO₃/CF, andNiOOH/Cu₂O/CF prepared under the conditions of Example 1, ComparativeExample 1, and Example 5. It can be found that the nickel oxide,oxidized cuprous, and tungsten oxide were grown in situ on the foamedcopper by a two-step method, and the oxygen defects in the product weresignificantly increased, which also further proved that NiOOH waseffective for the increase in content of oxygen defects, compared withCu₂O/WO₃/CF and NiOOH/Cu₂O/WO₃/CF composite materials.

FIG. 7 shows a comparative graph of the electrocatalytic hydrogenproduction overpotentials at different current densities forNiOOH/Cu₂O/WO₃/CF, Cu₂O/WO₃/CF, NiOOH/Cu₂O/CF, and CF prepared under theconditions of Example 1, Comparative Example 1, and Example 5. Theobtained electrocatalytic materials were respectively placed into aneutral electrolyte (1M KH₂PO₄+1M K₂HPO₄) for electrocatalytic testing.It can be seen that the NiOOH/Cu₂O/WO₃/CF electrocatalytic compositematerial with rich oxygen defect prepared by the present disclosure hadthe smallest overpotential under different current densities, and itssurface had the best hydrogen production performance. At high currentdensities of 100, 200, 300, 400, and 500 mA/cm², its overpotentials wererespectively 294, 386, 464, 533, and 589 mV.

1. A Cu₂O/WO₃/CF self-supporting electrocatalytic material, comprising:a foamed copper substrate, and Cu₂O and WO₃ grown in situ on the foamedcopper substrate.
 2. The Cu₂O/WO₃/CF self-supporting electrocatalyticmaterial according to claim 1, wherein the total loading capacity ofCu₂O and WO₃ is 0.5 to 4 mg/cm².
 3. The Cu₂O/WO₃/CF self-supportingelectrocatalytic material according to claim 1, wherein the molar ratioof WO₃ and Cu₂O is 1:(0.5 to 1).
 4. The Cu₂O/WO₃/CF self-supportingelectrocatalytic material according to claim 1, wherein the Cu₂O/WO₃/CFself-supporting electrocatalytic material also includes NiOOH grown insitu on the foamed copper substrate.
 5. The Cu₂O/WO₃/CF self-supportingelectrocatalytic material according to claim 4, wherein the totalloading capacity of NiOOH, Cu₂O, and WO₃ in the Cu₂O/WO₃/CFself-supporting electrocatalytic material is 0.5 to 4 mg/cm².
 6. TheCu₂O/WO₃/CF self-supporting electrocatalytic material according to claim4, wherein the molar ratio of WO₃, Cu₂O and NiOOH is 1:(0.5 to 1):(0.01to 0.05).
 7. A preparation method of the Cu₂O/WO₃/CF self-supportingelectrocatalytic material of claim 1, comprising: (1) dissolving atungsten source in absolute ethanol to obtain a first solution; and (2)immersing the foamed copper in a high-pressure reaction kettlecontaining the first solution, reacting at 100 to 200° C. for 1 to 36hours, and then centrifuging, washing, and drying to obtain theCu₂O/WO₃/CF self-supporting electrocatalyst material.
 8. A preparationmethod of the Cu₂O/WO₃/CF self-supporting electrocatalytic material ofclaim 4, comprising: (1) dissolving a tungsten source in absoluteethanol to obtain a first solution; and (2) immersing the foamed coppergrown with NiOOH and Cu₂O in a high-pressure reaction kettle containingthe first solution, reacting at 100 to 200° C. for 1 to 36 hours, andthen centrifuging, washing, and drying to obtain a NiOOH/Cu₂O/WO₃/CFself-supporting electrocatalytic material.
 9. The preparation methodaccording to claim 8, wherein the foamed copper grown with NiOOH andCu₂O is prepared by: (1) dissolving a nickel source in water to obtain asecond solution; and (2) immersing the foamed copper in a high-pressurereaction kettle containing the second solution, reacting at 160 to 200°C. for 6 to 12 hours, and then washing and drying to obtain the foamedcopper with NiOOH and Cu₂O.
 10. The preparation method according toclaim 9, wherein the nickel source is selected from at least one ofnickel acetate Ni(CH₃COO)₂, nickel oxalate dihydrate NiC₂O₄.2H₂O, nickelchloride hexahydrate NiCl₂.6H₂O, and nickel nitrate hexahydrateNiN₂O₆.6H₂O, the concentration of the nickel source is 0.01 to 5 mol/L,and the volume filling ratio of the high-pressure reaction kettlecontaining the second solution is 20 to 80%.
 11. The preparation methodaccording to claim 7, wherein the tungsten source is selected from atleast one of ammonium tungstate (NH₄)₆W₇O₂₄.6H₂O, ammonium paratungstate(NH₄)₁₀[H₂W₁₂O₄₂], ammonium metatungstate (NH₄)₆H₂W₁₂O₄₀, tungstenisopropoxide W(OCH(CH₃)₂)₆, and tungsten hexachloride WCl₆, and theconcentration of the tungsten source in the first solution is 0.01 to 5mol/L.
 12. The preparation method according to claim 7, wherein thevolume filling ratio of the high-pressure reaction kettle containing thefirst solution is 20 to 60%.